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1
Loghin, Daniel. "Green's functions for preconditioning." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325147.
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Tookos, Ferenc. "Holder continuity of green's functions." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0001137.
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Harwood, Adrian Roy George. "Numerical evaluation of acoustic Green's functions." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/numerical-evaluation-of-acoustic-greens-functions(809386ea-59cb-453b-9770-5e3250b35e98).html.
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The reduction of noise generated by new and existing engineering products is of increasing importance commercially, socially and environmentally. Commercially, the noise emission of vehicles, such as cars and aircraft, may often be considered a selling point and the effects of noise pollution on human health and the environment has led to legislation restricting the noise emissions of many engineering products. Noise prediction schemes are important tools to help us understand and develop a means of controlling noise. Acoustic problems present numerous challenges to traditional CFD-type numerical methods rendering all but the most trivial problems unsuitable. Difficulties relate to the length scale discrepancies which arise due to the relatively tiny pressure and density fluctuations of an acoustic wave propagating over large distancesto the point of interest; the result being large computational domains to capture wave behaviour accurately between source and observer. Noise prediction may be performed using a hybrid Computational Aero-Acoustics (CAA) scheme, an approach to noise prediction which alleviates many issues associated with exclusively numerical or analytical approaches. Hybrid schemes often rely on knowledge of a Green’s function, representing the scattering of the geometry, to propagate source fluctuations to the far-field. Presently, these functions only exist in analytical form for relatively simple geometries. This research develops principles for the robust calculation of Green’s functions for general situations. In order to achieve this, three techniques to computeGreen’s functions for the Helmholtz equation within an extended class of 2D geometries are developed, evaluated and compared. Where appropriate, their extension to 3D is described. Guidance is provided on the selection of a suitable numerical method in practice given knowledge of the geometry of interest. Through inclusion of the numerical methods for the construction of Green’s functions presented here, the applicability of existing hybrid schemes will be significantly extended. Thus, it is expected that noise predictions may be performed on a more general range of geometries while exploiting the computational efficiency of hybrid prediction schemes.
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Pearson, Gary S. "Strain Green's functions for buried quantum dots." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/2385/.
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Argani, Luca Prakash. "Dislocations and Green's functions in prestressed solids." Doctoral thesis, Università degli studi di Trento, 2014. https://hdl.handle.net/11572/367724.
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The present Ph.D. dissertation is divided into two Parts: Green's function and problems of the inclusions and dislocations are addressed in the first Part, while implementation of elastoplastic constitutive laws are treated in the second.
These subjects can be seen as different approaches to the investigation of the plastic behaviour of materials.
In the first Part, infinite-body two-dimensional Green's functions are derived for the incremental deformation of an incompressible, anisotropic, prestressed body.
These functions, given by Bigoni and Capuani, show the response of an infinite body to a concentrated force.
The effect of prestress on dislocation (and inclusion) fields in non-linear elastic solids is analyzed by extending previous solutions by Eshelby and Willis.
Employing a plane strain constitutive model (for incompressible incremental non-linear elasticity) to describe the behaviour a broad class of (anisotropic) materials, but with a special emphasis on ductile metals (J2-deformation theory of plasticity), it is shown that strongly localized strain patterns emerge, when a dislocation dipole is emitted by a source and the prestress level is high enough.
These strain patterns may explain cascade activation of dislocation clustering along slip band directions.
Several of the presented results remain valid within a three-dimensional context.
Novel infinite-body three-dimensional Green's functions are derived for the incremental deformation of an incompressible, anisotropic, prestressed body.
The case of a force dipole is developed within this framework.
Results are used to investigate the behaviour of a material deformed near the limit of ellipticity loss and to reveal features related to shear failure cones development in a three-dimensional solid medium.
Non-standard elastoplastic constitutive laws are treated in the second Part of the present Ph.D. dissertation, based on pressure-sensitive yield functions, such that proposed by Bigoni and Piccolroaz, which describes the inelastic deformation of ceramic powders and of a broad class of rock-like and granular materials.
This yield function is not defined outside the yield locus, so that 'gradient-based' integration algorithms of elastoplasticity cannot be directly employed.
Therefore, two ad hoc integration algorithms are proposed: an explicit scheme based on a forward Euler technique with a 'centre-of-mass' return correction and an implicit scheme based on a 'cutoff-substepping' return algorithm.
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Argani, Luca Prakash. "Dislocations and Green's functions in prestressed solids." Doctoral thesis, University of Trento, 2014. http://eprints-phd.biblio.unitn.it/1213/1/Argani-Luca_PhD-Thesis_3D_EN-IT_embedded.pdf.
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The present Ph.D. dissertation is divided into two Parts: Green's function and problems of the inclusions and dislocations are addressed in the first Part, while implementation of elastoplastic constitutive laws are treated in the second.
These subjects can be seen as different approaches to the investigation of the plastic behaviour of materials.
In the first Part, infinite-body two-dimensional Green's functions are derived for the incremental deformation of an incompressible, anisotropic, prestressed body.
These functions, given by Bigoni and Capuani, show the response of an infinite body to a concentrated force.
The effect of prestress on dislocation (and inclusion) fields in non-linear elastic solids is analyzed by extending previous solutions by Eshelby and Willis.
Employing a plane strain constitutive model (for incompressible incremental non-linear elasticity) to describe the behaviour a broad class of (anisotropic) materials, but with a special emphasis on ductile metals (J2-deformation theory of plasticity), it is shown that strongly localized strain patterns emerge, when a dislocation dipole is emitted by a source and the prestress level is high enough.
These strain patterns may explain cascade activation of dislocation clustering along slip band directions.
Several of the presented results remain valid within a three-dimensional context.
Novel infinite-body three-dimensional Green's functions are derived for the incremental deformation of an incompressible, anisotropic, prestressed body.
The case of a force dipole is developed within this framework.
Results are used to investigate the behaviour of a material deformed near the limit of ellipticity loss and to reveal features related to shear failure cones development in a three-dimensional solid medium.
Non-standard elastoplastic constitutive laws are treated in the second Part of the present Ph.D. dissertation, based on pressure-sensitive yield functions, such that proposed by Bigoni and Piccolroaz, which describes the inelastic deformation of ceramic powders and of a broad class of rock-like and granular materials.
This yield function is not defined outside the yield locus, so that 'gradient-based' integration algorithms of elastoplasticity cannot be directly employed.
Therefore, two ad hoc integration algorithms are proposed: an explicit scheme based on a forward Euler technique with a 'centre-of-mass' return correction and an implicit scheme based on a 'cutoff-substepping' return algorithm.
7
Lin, Chung-Yi. "Nonlinear Green's function theory of disordered material /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487585645575385.
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Carbone, Arianna. "Self-consistent Green's functions with three-body forces." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/133260.
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The quantum many-body problem is an everlasting challenge for theoretical physics. The aim sought is to analyze, at the quantum level, the observables arising from a group formed by a certain number of interacting particles N. In the specific case of nuclear physics, the study and interpretation of interacting nuclear systems has spanned from the finite nuclei to the infinite nuclear matter case. In order to characterize such systems, the forces with which nucleons interact in their interior need to be sorted out. Once the Hamiltonian is chosen, the many-body problem for the group of interacting fermions, the nucleons, has to be solved.
In the present thesis we focus our study on infinite nuclear matter, analyzing the properties of the two systems which stand at the extremes in terms of isospin asymmetry: symmetric nuclear matter (SNM), with an equal number on neutrons and protons, and pure neutron matter (PNM), with only neutrons. We base our approach in terms of realistic microscopic potentials, hence we need to choose a many-body technique in order to treat the potential. We choose to perform our calculations exploiting the formalism provided by the self-consistent Green's function's (SCGF) theory. This approach is based on a diagrammatic expansion of the single-particle (SP) Green's function, or propagator. This method was devised to treat the correlated, i.e. beyond mean-field, behavior of strongly interacting systems, such as nuclear matter.
Unfortunately, it is a well established fact that whatever microscopic two-nucleon forces (2NFs) are used in the many-body calculation, empirical saturation properties of nuclear matter fail to be reproduced. Saturation densities appear at high values, presenting energies which are inconsistently too attractive, overbinding nuclear matter. This inconsistency bears some similarities to the case of light nuclei where, on the contrary, the 2NF-only based theory underbinds experimental data. The inclusion of three-nucleon forces (3NFs) has been the indispensable factor to cure this deficiency. Hence,
microscopic 3NFs have been mostly devised to provide attraction in light finite systems, small densities, and repulsion in infinite systems, high densities. However, in modeling these 3NFs, the inclusion of phenomenological ingredients has often been the way followed. To bypass the need to adjust the potential with ad hoc contributions, an alternative has been provided by chiral effective field theory (EFT).
Featuring the consistent Hamiltonian at the 2N and 3N level provided by EFT, in this thesis we present calculations including both chiral 2NFs and 3NFs. This is dealt within an extended SCGF formalism, specifically formulated to include consistently 3B forces by means of effective interactions.
We observe the striking effect of the inclusion of 3N forces for the total energy of the many-body ground state. Exploiting the extended SCGF approach presented in this thesis, we see how the modifications induced by the 3B force are larger as the density increases. This increasing with density is what provides the saturation mechanism for nuclear matter. In pure neutron matter, 3NFs are the main cause for the stiffening of the equation of state. In view of astrophysical studies for neutron star masses, this stiffening is a major ingredient for the achievement of theoretical results which can better match recent astrophysical observations.
The idea, on which the development of this thesis was based, has been all the way the quest to introduce consistently three-body forces in the formalism of the SCGF theory. While the main motivation of this study has been nuclear systems, the extended SCGF formalism can be easily applied to other many-body systems, of either atomic or molecular nature.<br>El problema quàntic de molts cossos ha estat sempre un repte de la física teòrica. L'objectiu al qual s'intenta arribar es la descripció, des d'un punt de vista quàntic, dels observables d'un sistema de moltes partícules en interacció. En el camp específic dels sistemes nuclears, dels més petits com els nuclis als més grans com la matèria nuclear infinita dins de les estrelles, el problema nuclear de molts cossos s'ha intentat resoldre amb la construcció de diferents formalismes. L'objectiu ha sigut descriure aproximadament el comportament de molts nucleons, obtenen resultats els més propers als experimentals i empírics.
En la present tesis ens hem centrat sobre l'estudi de la matèria nuclear infinita. En particular sobre els dos sistemes infinits que es situen en els extrems en termes d'asimetria d'isospín: la matèria nuclear simètrica (SNM), el sistema format d'un igual nombre de protons i nucleons, i la matèria purament neutrónica (PNM), el sistema format solament de neutrons.
Per dur a terme aquests càlculs hem expandit, de manera consistent, el formalisme de funcions de Green auto-consistents per incloure forces a tres cossos. Hem treballat amb un potencial basat en la teoria efectiva de baixes energies aplicada a la Cromodinàmica Quàntica (QCD), i.e. la teoria efectiva quiral. En aquesta teoria, les 2NFs i 3NFs apareixen consistentment.
La inclusió de les forces a tres cossos en els càlculs s'ha demostrat ser fonamental per obtenir el mecanisme de saturació en SNM al voltant de valors acceptables d'energia/densitat i per proporcionar una equació d'estat més rígida per al sistema de PNM. Això demostra, un cop més, la necessitat de considerar les forces de molts cossos per fel càlculs teòrics consistents amb els resultats empírics i experimentals.
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Sternbeck, André. "The infrared behavior of lattice QCD green's functions." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15527.
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Diese Arbeit untersucht im Rahmen der Gittereichtheorie verschiedene Aspekte der QCD in der Landau-Eichung, insbesondere solche, die mit den Gluon- und Geist-Propagatoren bei kleinen Impulsen zusammenhängen. Die Eichgruppe ist SU(3). Wir analysieren den Einfluss unterschiedlicher systematischer Effekte. Wir zeigen, dass der Formfaktor des Geist-Propagators bei kleinen Impulsen systematisch von der Wahl der Eichkopien (Gribov-Kopien) abhängt. Hingegen können wir einen solchen Einfluss auf den Gluon-Propagator nicht feststellen. Ebenfalls wird die Verteilung der kleinsten Eigenwerte des Faddeev-Popov-Operators durch die Wahl der Eichkopien beeinflusst. Wir zeigen außerdem, dass der Einfluss dynamischer Wilson-Fermionen auf den Geist-Propagator für die untersuchten Impulse vernachlässigbar ist. Für den Gluon-Propagator können wir jedoch einen deutlichen Einfluss für große und mittlere Impulse feststellen. Zusätzlich wurden beide Propagatoren auf asymmetrischen Gittern gemessen und mit den Daten von symmetrischen Gittern verglichen. Wir vergleichen unsere Ergebnisse mit denen aus Studien von Dyson-Schwinger-Gleichungen für den Gluon- und Geist-Propagator. Wir zeigen, dass das in dieser Arbeit gefundene Niedrigimpulsverhalten im Einklang mit verschiedenen Kriterien für Confinement (Einschluss von Farbladungen) ist. Wir berechnen die laufende Kopplung, die sich als eine renormierungsgruppeninvariante Kombination der Gluon- und Geist-Formfaktoren ergibt. Unsere Ergebnisse zeigen, dass im Bereich kleiner Impulse die laufende Kopplung kleiner wird und so vermutlich kein endlicher Infrarot-Fixpunkt im Grenzfall Impuls Null angestrebt wird. Wir präsentieren außerdem eine erste nichtstörungstheoretische Berechnung der Renormierungskonstante des SU(3) Ghost-Gluon-Vertex. Wir berichten über Untersuchungen zu spektralen Eigenschaften des Faddeev-Popov-Operators. Dazu haben wir eine Reihe der kleinsten Eigenwerte und Eigenvektoren dieses Operators berechnet.<br>Within the framework of lattice QCD we investigate different aspects of QCD in Landau gauge using Monte Carlo simulations. In particular, we focus on the low momentum behavior of gluon and ghost propagators. The gauge group is SU(3). Different systematic effects on the gluon and ghost propagators are studied. We demonstrate the ghost dressing function to systematically depend on the choice of Gribov copies at low momentum, while the influence on the gluon dressing function is not resolvable. Also the eigenvalue distribution of the Faddeev-Popov operator is sensitive to Gribov copies. We show that the influence of dynamical Wilson fermions on the ghost propagator is negligible at the momenta available to us. On the contrary, fermions affect the gluon propagator at large and intermediate momenta. In addition, we analyze data for both propagators obtained on asymmetric lattices and compare these results with data obtained on symmetric lattices. We compare our data with results from studies of Dyson-Schwinger equations for the gluon and ghost propagators. We demonstrate that the infrared behavior of both propagators, as found in this thesis, is consistent with different criteria for confinement. However, the running coupling constant, given as a renormalization-group-invariant combination of the gluon and ghost dressing functions, does not expose a finite infrared fixed point. Rather the data are in favor of an infrared vanishing coupling constant. We also report on a first nonperturbative computation of the SU(3) ghost-gluon-vertex renormalization constant. We present results of an investigation of the spectral properties of the Faddeev-Popov operator. For this we have calculated the low-lying eigenvalues and eigenmodes of the Faddeev-Popov operator.
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Choi, Ikguen. "An efficient representation for the planar microstrip Green's function." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1272977636.
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Mastin, Mark R. Benesh Gregory Allen. "An SEGF study of the Rh(001) surface." Waco, Tex. : Baylor University, 2007. http://hdl.handle.net/2104/5076.
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Kipp, Robert. "Mixed potential integral equation solutions for layered media structures : high frequency interconnects and frequency selective surfaces /." Thesis, Connect to this title online; UW restricted, 1993. http://hdl.handle.net/1773/5974.
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Roman, Svetlana. "Green's functions for boundary-value problems with nonlocal boundary conditions." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20111227_092148-01085.
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In the dissertation, second-order and higher-order differential and discrete equations with additional conditions which are described by linearly independent linear functionals are investigated. The solutions to these problems, formulae and the existence conditions of Green's functions are presented, if the general solution of a homogeneous equation is known. The relation between two Green's functions of two nonhomogeneous problems for the same equation but with different additional conditions is obtained. These results are applied to problems with nonlocal boundary conditions.
In the introduction the topicality of the problem is defined, the goals and tasks of the research are formulated, the scientific novelty of the dissertation, the methodology of research, the practical value and the significance of the results are presented.
m-order differential problem and its Green's function are investigated in the first chapter. The relation between two Green's functions and the existence condition of Green's function are obtained.
In the second chapter, the main definitions and results of the first chapter are formulated for the second-order differential equation with additional conditions. In the examples the application of the received results is analyzed for problems with nonlocal boundary conditions in detail.
In the third chapter, the second-order difference equation with two additional conditions is considered. The expression of Green's function and its existence... [to full text]<br>Disertacijoje tiriami antros ir aukštesnės eilės diferencialinis ir diskretusis uždaviniai su įvairiomis, tame tarpe ir nelokaliosiomis, sąlygomis, kurios yra aprašytos tiesiškai nepriklausomais tiesiniais funkcionalais. Pateikiamos šių uždavinių Gryno funkcijų išraiškos ir jų egzistavimo sąlygos, jei žinoma homogeninės lygties fundamentalioji sistema. Gautas dviejų Gryno funkcijų sąryšis uždaviniams su ta pačia lygtimi, bet su papildomomis sąlygomis. Rezultatai pritaikomi uždaviniams su nelokaliosiomis kraštinėmis sąlygomis.
Įvadiniame skyriuje aprašyta tiriamoji problema ir temos objektas, išanalizuotas temos aktualumas, išdėstyti darbo tikslai, uždaviniai, naudojama tyrimų metodika, mokslinis darbo naujumas ir gautų rezultatų reikšmė, pateikti ginamieji teiginiai ir darbo rezultatų aprobavimas.
m-tosios eilės diferencialinis uždavinys ir jo Gryno funkcija nagrinėjami pirmajame skyriuje. Surastas uždavinio sprendinys, išreikštas per Gryno funkciją. Pateikta Gryno funkcijos egzistavimo sąlyga.
Antrajame skyriuje pateikti pirmojo skyriaus pagrindiniai apibrėžimai ir rezultatai antros eilės diferencialinei lygčiai. Pavyzdžiuose išsamiai išanalizuotas gautų rezultatų pritaikymas uždaviniams su nelokaliosiomis kraštinėmis sąlygomis.
Trečiajame skyriuje nagrinėjama antros eilės diskrečioji lygtis su dviem sąlygomis. Surastos diskrečiosios Gryno funkcijos išraiška ir jos egzistavimo sąlyga. Taip pat pateiktas dviejų Gryno funkcijų sąryšis, kuris leidžia surasti diskrečiosios... [toliau žr. visą tekstą]
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Xu, Jiandong. "Multi-region boundary element analysis and multi-layered Green's functions." Thesis, University of Glasgow, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443406.
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Ellis, Robert B. "Chip-firing games with Dirichlet eigenvalues and discrete Green's functions /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3061630.
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Steiner, Jean. "Green's functions, spectral invariants, and a positive mass on spheres /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3091324.
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Mercier, Jean-Philippe. "Improved teleseismic Green's functions and western Canada mantle structure and evolution." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2779.
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The present thesis is divided into three distinct parts and focuses both on the improvement of deconvolution technique in a teleseismic context for crustal and upper-mantle studies and on the understanding of western Canada structure and evolution through seismic imaging. The first part presents estimates of the P-component of the teleseismic-P Green's functions for three stations of the Canadian National Seismic Network (CNSN) obtained using a new deconvolution technique. Our results show evidence of the principal, first-order scattered Moho phases and, in particular, the Pp_Mp. The second part presents teleseismic receiver functions from 20 broadband three-component seismometers deployed along the MacKenzie-Liard Highway in Canada's Northwest Territories as part of the joint Lithoprobe-IRIS CAnadian NOrthwest Experiment (CANOE). These stations traverse a Paleoproterozoic suture and subduction zone that has been previously documented in detail to mantle depths using seismic reflection profiling. Our results reveal the response of the ~1.8 Ga subduction zone on both the radial and transverse component. The identification of this structure and its comparison with fine-scale mantle layering below the adjacent Slave province and from a range of Precambrian terranes provides an unambiguous connection between fossil subduction and fine-scale, anisotropic mantle layering found beneath cratons. Previous documentation of similar layering below the adjacent Slave province provides strong support for the thesis that early cratonic blocks were stabilized through processes of shallow subduction. The last part presents P- and S wave velocity models for western Canada. In this part, we focus our attention on two distinct features: 1) the transition from Phanerozoic to cratonic mantle in northwestern Canada and 2) the complex tectonic environment at the northern terminus of the Cascadia subduction zone where the plate boundary changes from convergent to transform. We find that the main transition from Phanerozoic to cratonic mantle in northwestern Canada occurs at the Cordilleran deformation front. In northern Cascadia, we have imaged and characterized the signature of the subducting Juan de Fuca plate and observed evidence of subduction beyond the northern edge of the slab. Our result show that the Anahim hotspot track is underlain by a -2% low-velocity zone.
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Mathews, James Richard. "Mathematical modelling of noise generation in turbofan aeroengines using Green's functions." Thesis, University of Cambridge, 2016. https://www.repository.cam.ac.uk/handle/1810/264140.
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With demand for aircraft travel set to double in the next twenty years, targets are in place to reduce noise levels and emissions. For example, one target is that the effective perceived noise from aircraft in 2020 should be half of the 2000 level. One of the key noise components is the aeroengine. Building and designing an aeroengine costs millions of pounds and furthermore, to prove the aeroengine is safe, it has to be tested to destruction. Engineers and mathematicians are employed to design aeroengines that will not only be quieter but more fuel efficient and produce fewer harmful emissions while maintaining or improving performance. The main topic of this thesis is investigating rotor-stator interaction which occurs when the turbulent, swirling air produced by the rotor hits the stator and generates noise. We do this in two distinct ways, firstly we calculate the Green’s function for pressure in a turbofan duct with swirling mean flow and secondly we investigate the effect of turbulence hitting an isolated aerofoil. The Green’s function allows engineers to calculate the noise from rotor-stator interaction in simple cases and can be used in beamforming to analyse noise sources in the aeroengine. We consider an infinite duct, and use the Euler equations to derive a sixth order partial differential equation for pressure in the duct. We then find a Green’s function of this equation, which can be done numerically or analytically using high-frequency asymptotics. Our main interest is the analytic Green’s function, which we compare to numerical results. We begin by assuming the base flow has shear and swirling components in a constantly lined duct, and our analytic Green’s function is a new result. We then calculate the Green’s function for a base flow with variable entropy and a lining that varies with circumferential position. To consider flow-blade interaction we simulate the turbulent wake of the rotor hitting a single stator blade. Tests in wind tunnels have shown that, depending on the parameters, introducing a serration on the leading edge of the aerofoil can reduce the noise significantly. We build an analytical model to investigate the effect of the serrated edge, which again involves solving a differential equation by using a Green’s function. It also requires modelling the turbulence, which we do by using either deterministic eddies or stochastic eddies. We show it is possible to reduce the noise by using a serrated leading edge, but it is hard to predict the correct choice of serration to minimise the noise.
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Aryasomayajula, Naga Venkata Anilatmaja. "Bounds for Green's functions on hyperbolic Riemann surfaces of finite volume." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2013. http://dx.doi.org/10.18452/16828.
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Im Jahr 2006, in einem Papier in Compositio Titel "Bounds auf kanonische Green-Funktionen" J. Jorgenson und J. Kramer, haben optimale Schranken für den hyperbolischen und kanonischen Green-Funktionen auf einem kompakten hyperbolischen Riemannschen Fläche definiert abgeleitet. Diese Schätzungen wurden im Hinblick auf abgeleitete Invarianten aus hyperbolischen Geometrie der Riemannschen Fläche. Als Anwendung abgeleitet sie Schranken für die kanonische Green-Funktionen durch Abdeckungen und für Familien von Modulkurven. In dieser Arbeit erweitern wir ihre Methoden nichtkompakten hyperbolischen Riemann Oberflächen und leiten ähnliche Schranken für den hyperbolischen und kanonischen Green-Funktionen auf einem nichtkompakten hyperbolischen Riemannschen Fläche definiert.<br>In 2006, in a paper in Compositio titled "Bounds on canonical Green''s functions", J. Jorgenson and J. Kramer have derived optimal bounds for the hyperbolic and canonical Green''s functions defined on a compact hyperbolic Riemann surface. These estimates were derived in terms of invariants coming from hyperbolic geometry of the Riemann surface. As an application, they deduced bounds for the canonical Green''s functions through covers and for families of modular curves. In this thesis, we extend their methods to noncompact hyperbolic Riemann surfaces and derive similar bounds for the hyperbolic and canonical Green''s functions defined on a noncompact hyperbolic Riemann surface.
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Wendoloski, John Chester. "Applications of Green's functions to acoustic ducts and cavities with rigid boundaries." Thesis, The University of Sydney, 1995. https://hdl.handle.net/2123/26904.
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The present work is concerned with descriptions of acoustic wave behaviour in the presence of rigid boundaries. The unifying theme of this work is the application of Green’s function techniques to a selection of duct and cavity problems in acoustics. Although the central theme of this thesis is theoretical, experiments are also performed to test the validity of the theory. The thesis covers two basic areas: the diffraction of sound in cylindrical pipes fitted with flanges and orifice plates; and the inverse acoustics of rigid rectangular cavities.
The diffraction of sound from flanged cylindrical waveguides is a classical problem in acoustics. Chapter 2 deals with the initial work on this subject. In this chapter, non—dissipative, inviscid, linear wave theory is compared with experiment and some of the mathematical formulations of this problem by previous authors are unified. A central problem with the ‘classical’ theory is the prediction of velocity singularities at sharp edges.
In Chapter 3, the diffraction of sound is considered in a cylindrical duct with a thin orifice plate blockage, in the presence of a mean flow. Viscosity in the fluid produces vorticity, the strength of which may be determined by the requirement that the fluid velocity at the orifice rim be finite. Theoretical analysis is performed based on this principle. Numerical calculations are made for various physical parameters and an experiment is performed to test the predictions of the theory.
Chapter 4 deals with inverse wave problems in a rigid rectangular, two dimensional cavity. The primary emphasis of this chapter is on reconstructing a spatially incoherent random source within a rigid rectangular cavity by pressure measurements on the cavity walls. The related problem of reconstructing a deterministic point source under these conditions is also addressed. Two other formalisms are derived. Again, they are both set in a rigid rectangular cavity. The first of these is a method for iteratively reconstructing a source profile. The second formalism concerns the problem of reconstructing a rigid scatterer under the restriction of the first Born approximation.
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Yeo, Stephen K. N. "Generalised periodic Green's function analysis of microstrip dipole arrays /." Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phy46.pdf.
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Watrous, Mitchell James. "Finite temperature densities via the Green's-function method with application to electron screening in plasmas /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/9705.
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Kurcz, Christopher. "Fast convolutions with Helmholtz Green's functions and radially symmetric band-limited kernels." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3303887.
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Lani, Giovanna. "Towards a novel approach for the calculation of many-body Green's functions." Palaiseau, Ecole polytechnique, 2011. https://pastel.hal.science/docs/00/66/79/23/PDF/thesis-glani.pdf.
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Dans ce travail, une nouvelle voie pour le calcul de la fonction de Green (GF) à une particule a été développée. L' objectif est de remédier aux défauts de nombreuses autres approches à plusieurs corps, par exemple l'approximation GW (GWA), dans le traitement des forts effets de corrélation dans les solides. L'idée consiste à résoudre un ensemble d'équations différentielles fonctionnelles et non-linéaires, qui sont centrales à la théorie des perturbations à plusieurs corps. Dans un premier temps, ce qu'on appelle le modèle à un 1-point est employé (une seule valeur pour chaque variable d'espace, temps, spin est retenue) et l'ensemble des équations se réduit alorsà une seule équation algébrique, pour laquelle une solution exacte et explicite est obtenue. La solution est utilisée comme outil de référence pour analyser les performances des autres méthodes bien établies (par exemple, des versions différentes de GW). Par ailleurs, des approximations alternatives sont conçues et pour les plus prometteuses la généralisation à la forme fonctionnelle (complète) est discutée. La dernière partie de cetravail aborde la généralisation de l'approche au-delà du cadre à1-point. Tout d'abord la dépendance en fréquence de la GF est restaurée (tout en conservant le modèle à un 1-point pour les variables d'espace et despin) et l'ensemble des équations est résolu. Il est montré que dans un tel cadre, il est possible de retrouver ce que l'on appelle "l'expansion en cumulants" pour GF- une approximation qui va au-delà de GW et fournit des fonctions spectrales en bon accord avec les expériences de photo-émission. Enfin, à l'aide d'un ansatz, une famille de solutions pour les equations dans leur forme fonctionnelle est obtenue et des moyens sont proposés, allant bien au delà de l'état de l'art, afin d'obtenir des approximations pour celles ayant une signification physique<br>In this work, a novel route to the calculation of the one particle Green's function (GF) has been developed. Its aim is to remedy to the shortcomings of other many-body approaches, e. G. The GW approximation (GWa), in treating strong effects of correlation in solids. The idea consists of solving a set of non-linear, differential, functional equations, which are pivotal to many-body perturbation theory. In a first instance, a so called 1-point model is employed (only one value for each time, spin, spatial variable is retained) and the set of equations reduces to a single algebraic equation, for which an explicit exact solution is obtained. The solution is used as a benchmark tool to analyze the performances of established many-body methods (e. G. Different GW flavours), moreover alternative approximations are devised and for the most promising ones the generalization to their full functional form is discussed. The last part of the work deals with the generalization of the approach beyond the 1-point framework. First the frequency dependence of the GF is restored (while still retaining the 1-point approximation for the space and spin variables) and the set of equations is solved. It is shown that in such framework it is possible to recover the so-called cumulant expansion for the GF- an approximation which is beyond GW and provides accurate spectral functions for photo emission experiments. Finally, through an ansatz, a family of solution for the equations in their full functional form is obtained and routes to approximate the physical one, far beyond the present state-of-the-art, are proposed
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Fernandes, Imara Lima 1987. "Transporte quântico em nano-estruturas magnéticas." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/276943.
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Orientador: Guillermo Gerardo Cabrera Oyarzún<br>Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin<br>Made available in DSpace on 2018-08-27T21:31:38Z (GMT). No. of bitstreams: 1
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Previous issue date: 2015<br>Resumo: Esta tese de doutorado abordou principalmente o estudo teórico das propriedades de transporte dependente do spin em nanoestruturas magnéticas. As principais estruturas estudadas foram junções magnéticas de tunelamento e sistemas compostos por um arranjo de pontos quânticos acoplados a eletrodos ferromagnéticos. Com o intuito de obter propriedades físicas do sistema como, a corrente elétrica, a corrente de spin, a densidade local de estados, a ocupação média nos pontos quânticos e a corrente induzida por spin transfer-torque utilizamos o formalismo de funções de Green de não-equilíbrio. Na primeira parte deste trabalho, estudamos os efeitos da inversão do spin nas propriedades de transporte em junções de tunelamento. Para estes sistemas, o fenômeno da magnetorresistência tem origem na densidade de estados dos elétrons de condução dos eletrodos e mostramos que ela é fortemente afetada pela inversão do spin no tunelamento. Além disso, foi possível observar que a inversão do spin induz um spin-torqueadicional ao sistema. Na segunda parte deste trabalho, investigamos as propriedades de transporte em um sistema composto por dois pontos quânticos em forma de T acoplados a eletrodos ferromagnéticos. Com a mesma metodologia empregada anteriormente, encontramos que o aparecimento da ressonância de Fano e a formação de estados ligados dependem fortemente dos parâmetros do sistema. Explorando em detalhes o sistema, foi observado que é possível controlar a condutância elétrica do sistema através de um potencial de gate. Em particular, ao variar a posição do nível de energia do ponto quântico central é possível inverter a ressonância de Fano. Na última parte, apresentamos os resultados numéricos para o sistema considerando um ponto quântico com dois níveis de energia acoplado a dois eletrodos ferromagnéticos, e no interior do ponto quântico levamos em conta a interação e-e e a interação spin-órbita de Rashba. A interação de Rashba introduz a transição entre os níveis de energia com a inversão do spin, o que originou interessantes propriedades no transporte dependente do spin. Em particular, para eletrodos não magnéticos obtivemos que o acoplamento spin-órbita resultou na criação de corrente de spin polarizada<br>Abstract: In this work, we have studied the spin-dependent quantum transport in magnetic nanostructures. The main structures studied are magnetic tunneling junctions and systems composed of an arrangement of quantum dots coupled to ferromagnetic electrodes. Using the nonequilibrium Green's function techinique, we were able to calculate selected properties of the systems such as the electric current, the spin current, local density of states and the current-induced spin-transfer torque. In the first system, we have observed the effects of the spin-flip scattering in the transport properties considering tunneling junctions composed by an insulating layer between two ferromagnetic electrodes. The results obtained for this system showed that the magnetoresistance is related to density of state effects at the ferromagnetic electrodes, and we have found that it is strongly affected by the spin-flip scattering. Besides, we also observed that the spin-flip scattering gives rise to an additional spin-torque to the system. For the system composed of two quantum dots T-shaped electrodes coupled to ferromagnetic electrodes, we investigated the spin-dependent properties. We have observed that the appearance of the Fano resonance and the formation of bound states rely strongly on system parameters. Another interesting finding is the possibility to control the electrical conductance via a gate voltage. We figured out that changing the energy level of the central dot affected directly the Fano resonance peak intensities. Lastly, we have showed that for the system composed by a quantum-dot with two energy levels coupled to two ferromagnetic electrodes must be modified when the \textit{e-e} and the Rashba spin-orbit interaction are taken into account. The Rashba interaction induces level transitions with spin-flip resulting in interesting properties in the spin-dependent transport. We have found out that the spin-orbit interaction strongly contributes to the spin current even for non-magnetic electrodes<br>Doutorado<br>Física<br>Doutora em Ciências
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Marcotte, Étienne. "First principles theory for quantum transport : effects of strong correlation." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116102.
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In this work, we investigate effects of strong correlation to quantum transport from atomic first principles. In order to accomplish this task, we use a well established state-of-the-art formalism of quantum transport where density functional theory (DFT) is carried out within the Keldysh non-equilibrium Green's functions (NEGF). To deal with certain strong correlation phenomenon, we integrated an local density approximation plus Hubbard U (LDA+U) exchange-correlation potential into the existing NEGF-DFT formalism. The LDA+U potential correctly accounts for the electronic structure of correlated material. We will present the theory and numerical implementation associated with the NEGF-DFT-(LDA+U) in detail. Extensive tests on the well known correlated material FeO crystal have been carried out and results compared with previous literature as well as to experimental data.<br>We then apply our NEGF-DFT-(LDA+U) technique to investigate transport physics of spin resolved tunnelling in Fe/MgO/Fe magnetic tunnel junctions (MTJ). We found that interfacial oxygen atoms are enough to localise the 3d electrons of infacial Fe atoms due to strong correlation. This surprising result substantially changes quantum transport properties of the MTJ, in particular it reduces magnetic resistance ratio by about 33%. This strongly correlated physics is absent if the conventional local spin density approximation (LSDA) is used in the NEGF-DFT analysis. Results of LSDA and LDA+ U exchange-correlation potential will be compared. Furthermore, through investigating contributions to scattering states by various atomic orbitals, we clearly identify the reason why LDA+U changes quantum transport in both quantitative and qualitative ways. Finally, we believe this strongly correlated physics should be general in other MTJs involving different oxides.
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Villa-Giron, Jorge M. "Asymptotic near-to-far-zone transformation for periodic conformal antennas embedded in canonical stuctures." Diss., Connect to online resource - MSU authorized users, 2008.
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Thesis (Ph.D.)--Michigan State University. Electrical and Computer Engineering, 2008.<br>Title from PDF t.p. (viewed on Mar. 27, 2009) Includes bibliographical references (p. 96-99). Also issued in print.
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Chen, Shuguang, and 陈曙光. "Nonequilibrium Green's function-hierarchical equation of motion method for time-dependent quantum transport." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206344.
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The nonequilibrium Green’s function-hierarchical equation of motion (NEGFHEOM) method has been developed to simulate the time-dependent electron transport process. The real-time evolution of the reduced single-electron density matrix is solved through the Liouville-von-Neumann equation. The method is very efficient compared to conventional NEGF formulas which need to discretize the simulation time. The hierarchical equation of motion (HEOM) is closed at the second-tier in the time-dependent noninteracting Kohn-Sham framework. When combined with the wide band limit (WBL) approximation, the HEOM terminate at the first-tier. The resulting NEGF-HEOM-WBL method is particularly suitable for simulating the long time transient dynamics for large systems.
The method developed is first applied to calculate the transient current through an array of as many as 1000 quantum dots. Upon switching on the bias voltage, the current increases linearly with respect to time before reaching its steady state value. And the time required for the current to reach its steady state value is exactly the time for a conducting electron to travel through the array at Fermi velocity. These phenomena can be understood by simple analysis on the energetics of the quantum dots or by classical electron gas model.
Then the method is employed to investigate several simple molecular circuits, in which the para-linkage or meta-linkage benzene acts as the transmitting molecular entity. The simulation results shows that it takes a certain amount of time before the quantum interference manifests itself, and that the transmission through the meta case is hundreds of times smaller than that through the para case. To investigate the quantum interference process in molecular electronics, the concept of Büttiker probe is introduced. The Büttiker probe is an electrode that, when attached to electronic devices, causes the coherence passing through disappear. Simulation results show that the Büttiker probe can enhance the transmission of the meta benzene system through destroying the constructive interference. By turning the probe on and off, it can be observed that large strong correlations are indeed built up as electrons are transported through benzenoid structures - when the decoherence is turned off, the current rises, and when the decoherence is turned back on, the current falls.
Finally, TDDFT(B)-NEGF-HEOM-WBL method is implemented to solve realistic systems in the formalism of time-dependent density functional theory (tightbinding). Ab initio calculations are carried out to simulate the time-dependent electron transport through a CNT-based device. The simulation results show that when the input bias voltage is in low frequency, both the conventional adiabatic approximation method and the NEGF-HEOM-WBL methods are good enough. However, when high frequency dynamic responses are need to be captured, the NEGF-HEOM-WBL method is more suitable.<br>published_or_final_version<br>Chemistry<br>Doctoral<br>Doctor of Philosophy
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Gunda, Rajendra. "Harmonic Green's functions of wedges and polygonal plates using the ray tracing technique /." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487949150070192.
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Dooley, Roger Benesh Greg. "Surface magnetism of Ni(001), Co(001), and Fe(001) an embedding Green function approach /." Waco, Tex. : Baylor University, 2007. http://hdl.handle.net/2104/5051.
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Perez, Eduardo G. "Analytical solution to the wave equation with discrete pressure sources a model for the Rijke tube /." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5718.
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Thesis (Ph. D.)--West Virginia University, 2008.<br>Title from document title page. Document formatted into pages; contains x, 97 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 84-88).
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Han, Jung Hoon. "Dynamics of the compressible edge /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/9761.
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Di, Sabatino Stefano. "Reduced density-matrix functional theory : correlation and spectroscopy." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30137.
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Cette thèse traite de la description de la corrélation électronique et de la spectroscopie dans le cadre de la Théorie de la Fonctionnelle de la Matrice Densité Réduite (RDMFT). Dans la RDMFT, les propriétés de l'état fondamental d'un système physique sont des fonctionnelles de la matrice densité à un corps. Plusieurs approximations à la corrélation électronique ont été proposées dans la littérature. Beaucoup d'entre elles peuvent être reliés au travail de Müller, qui en a proposé une similaire à l'approximation Hartree-Fock mais qui peut produire des nombres d'occupation fractionnaires. Cela n'est pas toujours suffisant, notamment dans les matériaux fortement corrélés. Par ailleurs, l'expression des observables du système en terme de la matrice densité n'est pas toujours connue. Tel est le cas, par exemple, pour la fonction spectrale, qui est liée aux spectres de photoémission. Dans ce cas, il y a des annulations d'erreur entre l'approximation à la corrélation électronique et l'approximation à l'observable, ce qui affaiblit la théorie. Dans cette thèse, nous recherchons des approximations plus précises en exploitant le lien entre les matrices densité et les fonctions de Green. Dans la première partie de la thèse, nous nous concentrons sur la fonction spectrale. En utilisant le modèle de Hubbard, qui peut être résolu exactement, nous analysons les approximations existantes à cette observable et nous soulignons leurs points faibles. Ensuite, à partir de sa définition en terme de la fonction de Green à un corps nous dérivons une expression pour la fonction spectrale qui dépend des nombres d'occupation naturels et d'une énergie efficace qui prend en compte toutes les excitations du système. Cette énergie efficace dépend de la matrice densité à un corps ainsi que des ordres supérieurs. Des approximations simples à cette énergie efficace donnent des spectres précis dans des systèmes modèles dans des régimes à la fois de faible et de forte corrélation. Pour illustrer notre méthode sur les matériaux réels, nous calculons le spectre de photoemission du NiO massif: notre méthode donne une image qualitativement correcte dans la phase antiferromagnétique et dans la phase paramagnétique, contrairement aux méthodes de champ moyen utilisés actuellement, qui donnent un métal dans le dernier cas. La deuxième partie de la thèse est plus explorative et traite des phénomènes dépendant du temps dans la RDMFT. En général, l'évolution temporelle des matrices densité est donnée par la hiérarchie des équations de Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY), dans lequel l'équation du mouvement de la matrice densité a n corps est donnée en termes de la matrice densité à n+1 corps. La première équation de la hiérarchie relie la matrice densité à un corps à la matrice densité à deux corps. La tâche difficile est de trouver des approximations à la matrice densité à deux corps. Les approximations existantes sont des extensions adiabatiques des approximations de l'état fondamental. Nous explorons cette question en examinant de nouvelles approximations qui nous tirons de la théorie à plusieurs corps (MBPT) basée sur les fonctions de Green ainsi que de la solution exacte du modèle de Anderson à deux niveaux dans son état fondamental. Nos premiers résultats sur le modèle de Anderson soumis à divers champs externes montrent quelques caractéristiques intéressantes, qui suggèrent d'explorer davantage ces approximations aussi sur des systèmes modèles plus grands<br>This thesis addresses the description of electron correlation and spectroscopy within the context of Reduced Density-Matrix Functional Theory (RDMFT). Within RDMFT the ground-state properties of a physical system are functionals of the ground-state reduced density matrix. Various approximations to electron correlation have been proposed in literature. Many of them, however, can be traced back to the work of Müller, who has proposed an approximation to the correlation which is similar to the Hartree-Fock approximation but which can produce fractional occupation numbers. This is not always sufficient. Moreover, the expression of the observables of the system in terms of the reduced density matrix is not always known. This is the case, for example, for the spectral function, which is closely related to photoemission spectra. In this case there are error cancellations between the approximation to correlation and the approximation to the observable, which weakens the theory. In this thesis we look for more accurate approximations by exploiting the link between density matrices and Green's functions. In the first part of the thesis we focus on the spectral function. Using the exactly solvable Hubbard model as illustration, we analyze the existent approximations to this observable and we point out their weak points. Then, starting from its definition in terms of the one-body Green's function, we derive an expression for the spectral function that depends on the natural occupation numbers and on an effective energy which accounts for all the charged excitations. This effective energy depends on the one-body as well as higher-order reduced density matrices. Simple approximations to this effective energy give accurate spectra in model systems in the weak as well as strong-correlation regimes. To illustrate our method on real materials we calculate the photoemission spectrum of bulk NiO: our method yields a qualitatively correct picture both in the antiferromagnetic and in the paramagnetic phases, contrary to currently used mean-field methods, which give a metal in the latter case. The second part of the thesis is more explorative and deals with time-dependent phenomena within RDMFT. In general the time evolution of the reduced density matrices is given by the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy of equations, in which the equation of motion of the n-body reduced density matrix is given in terms of the (n + 1)-body reduced density matrix. The first equation of the hierarchy relates the one-body to the two-body reduced density matrix. The difficult task is to find approximations to the two-body reduced density matrix. Commonly used approximations are adiabatic extension of ground-state approximations. We explore this issue by looking at new approximations derived from Many-Body Perturbation Theory (MBPT) based on Green's functions as well as from the exact solution of the two-level Anderson impurity model in its ground state. Our first results on the two-level Anderson model subjected to various external fields show some interesting and, at the same time, puzzling features, which suggest to explore further these approximations
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De, Lauretis Maria. "Transmission line theory for cable modeling: a delay-rational model based on Green's functions." Licentiate thesis, Luleå tekniska universitet, EISLAB, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26517.
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At present, induction motors are controlled via the so-called variable-frequency drives (VFD) that allow to control the speed for the motors. The purpose of this PhD thesis is to improve electromagnetic modeling techniques for the study of conducted electromagnetic emissions in variable-frequency drives, with the aim of enhancing their reliability in energy production plants. Pulse-width-modulated voltage converters are used to feed an AC motor, and they are considered to be the primary reason for high-frequency effects in both the motor and the supply grid. In particular, high-frequency currents, known as common mode currents, flow between all energized components and the ground and travel via low-resistance and low-inductance interconnects such as the power cable between the inverter and the motor.Electrically long power cables are commonly used in VFD installations, and require particular attention. Accurate models can be obtained using the theory of multiconductor transmission lines. In the case of nonlinear terminations, such as an inverter, only time-domain analysis is possible. In recent years, several techniques have been proposed. Some of these techniques include the lumped-element equivalent circuit method, the method of characteristics (MoC) and its generalizations, and the Pad´e approach. In this context, a modeling technique based on Green’s functions has been proposed. The input/output impedance matrix is expressed as a rational series, whose poles and their residues are identified by solving algebraic equations. The primary disadvantage of this method lies in the large number of poles that is typically necessary to model the dynamics of the system, especially when electrically long interconnectsare considered. To overcome this limitation, we have proposed the Delay-Rational Green’s-Function-based Method, abbreviated as DeRaG. In this method, the line delay is extracted and, by virtue of suitable mathematical manipulation of the rational series, is incorporated through hyperbolic functions. The delay extraction enables the use of a reduced number of poles and improves the accuracy of the model in general, avoiding any ringing effects in the time-domain response. The primary advantage of the proposed method compared with other well-known techniques lies in the delayed state-space representation. The obtained model can be computed regardless of the terminations and/or sources, and the terminal conditions can be immediately and essentially incorporated.The next step will be to simulate the entire inverter-cable-motor system. The partial element equivalent circuit (PEEC) technique will be used to model the interconnects as well as the discontinuities in the power cable that can be caused, for example, by switch disconnectors. The theoretical results will be verified against experimental measurements. The final objective is to provide new techniques for modeling the electrodynamics of variable-frequency drives to allow their complete EMC assessment as early as the design stage and to enable the planning of corrective actions in advance.<br><p>Godkänd; 2016; 20160318 (mardel); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Maria De Lauretis Ämne: Industriell Elektronik/Industrial Electronics Uppsats: Transmission Line Theory for Cable Modeling: A delay-rational model based on Green’s functions Examinator: Professor Jonas Ekman, Institutionen för system- och rymdteknik, Avdelning: EISLAB, Luleå tekniska universitet. Diskutant: Professor Sven Nordebo, Institutionen för fysik och elektroteknik, Linnéuniversitetet, Växjö. Tid: Tisdag 3 maj, 2016 kl 10.30 Plats: A1547, Luleå tekniska universitet</p><br>Frekvensomriktares funktion i beredskapskritiska system
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Morton, David Lee Stoddard Elizabeth P. "Methodology of a self-consistent Green's functions approach in nuclear matter at finite temperature." Diss., UMK access, 2007.
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Thesis (M.S.)--Dept. of Physics. University of Missouri--Kansas City, 2007.<br>"A thesis in physics." Typescript. Advisor: Elizabeth P. Stoddard. Vita. Title from "catalog record" of the print edition Description based on contents viewed Dec. 18, 2007. Includes bibliographical references (leaf 29). Online version of the print edition.
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del, Hougne Marc Philipp. "Shaping Green's Functions in Cavities with Tunable Boundary Conditions : From Fundamental Science to Applications." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC111.
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Cette thèse étudie le façonnage de champs électromagnétiques micro-ondes dans des cavités présentant des conditions aux limites reconfigurables. Le dispositif expérimental s'appuie sur une metasurface électroniquement reconfigurable qui couvre partialement les parois d'une cavité et qui permet ainsi de contrôler la façon dont les ondes y sont réfléchies. Le premier chapitre explore des aspects fondamentaux. D’abord, une étude paramétrique du façonnage d'un champ d'ondes électromagnétiques monochromatique et stationnaire en cavité est proposée en fonction d'un degré de contrôle introduit. Selon la valeur de ce paramètre, il est possible de concentrer de l'énergie en un endroit donné de la cavité de façon prédictible, de reconfigurer totalement cette cavité, ou bien de décider d'obtenir une résonance à une fréquence qui n'en supportait pas auparavant. Ensuite, l’imposition d’un comportement chaotique à une cavité de géométrie régulière est démontrée et une application au brassage des modes en chambre réverbérante est donnée. Dans la suite, la possibilité d’ajuster le couplage antenne-cavité est abordée, et une adaptation parfaite et dynamiquement configurable de l’impédance est proposée. Le reste du premier chapitre considère des champs transitoires. Dans un premier temps, la focalisation spatio-temporelle d’une impulsion fortement réverbérée dans une cavité en utilisant uniquement le contrôle spatial des ondes offert par la metasurface est démontrée, puis le lien avec le couplage entre les dégrées de liberté spatiaux et temporels du milieu de propagation est fait. Enfin, un dispositif permettant la reconfiguration répétée des conditions aux limites d'une cavité en un laps de temps inférieur au temps de vie des photons est réalisé, et des résultats préliminaires sont montrés. Dans le deuxième chapitre, des applications aux systèmes de communication sans fil multi-utilisateurs sont proposées. D’abord, dans la limite d’un bas facteur de qualité de la cavité, il est montré qu’un formalisme matriciel permet de décrire l’impact de la metasurface sur le champ. Cette matrice, mesurée sans information de phase, permet alors de focaliser le champ sur une ou plusieurs positions simultanément. Ensuite, la possibilité d’obtenir une diversité de canaux optimale (orthogonalité des canaux) en façonnant idéalement le désordre d’un milieu de propagation à l'aide de metasurfaces est établie. Finalement, le formalisme matriciel est utilisé afin d’introduire un concept de calcul analogique réalisé par le milieu désordonné en façonnant le front d’onde incident. Il est dès lors conclu qu’avec une infrastructure standard de Wi-Fi dans une maison, en combinaison avec une metasurface simple, cette idée peut être implémentée. Le concept est enfin transposé au domaine optique avec une fibre multimode. Au cours du troisième chapitre, quelques applications du façonnage d'ondes en milieux réverbérants aux capteurs des environnements connectés sont étudiées. D’abord, la possibilité de concentrer des champs électromagnétiques ambients sur des circuits redresseurs afin d’obtenir des tensions de sortie utiles est démontrée. De plus, grâce aux non-linéarités intrinsèques du redresseur, ceci est possible même sans avoir un retour direct du redresseur sur l’intensité du champ incident. Ensuite, un détecteur de mouvement hors ligne de vue et « intelligent » est proposé, qui profite d’un co-design de sa couche physique et du traitement de données. Enfin, il est démontré que même des objets non-coopératifs dans un environnement complexe peuvent être localisés grâce à leur contribution à la diffusion des ondes dans ledit milieu. L’équivalence d’utiliser la diversité fréquentielle ou bien le façonnage d’ondes dans ce contexte est établie<br>In this thesis, the shaping of microwave fields in chaotic cavities with tunable boundary conditions is studied experimentally. The experiments leverage a metasurface reflect-array that partially covers the cavity walls to tune the reverberation of waves inside the cavity. The first chapter explores several fundamental aspects. First, the achievable degree of control over stationary monochromatic wave fields is thoroughly investigated, and various regimes are identified, ranging from partial control over the wave field up to the limiting case of discrete resonances that can be tuned at wish. Next, the possibility to convert a cavity of regular geometry into one displaying chaotic characteristics by modulating the boundary conditions is examined and an application to non-mechanical mode-stirring in reverberation chambers is given. Then, the ability to tune the coupling between an antenna inside a cavity and the cavity itself is studied, revealing the opportunity of achieving (dynamically tunable) perfect impedance matching. The chapter goes on to consider spatio-temporal wave fields, and the re-focusing of such transient fields at a desired instant with the purely spatial control of the metasurface is demonstrated; moreover, the interplay of spatial and temporal degrees of freedom is addressed. Finally, an experimental platform enabling the rapid modulation of cavity boundary conditions within the photon lifetime is presented. The second chapter considers applications to multi-user wireless communication systems. First, it is shown that a matrix formalism to capture the impact of the metasurface on the wave field can be formulated in the regime of low reverberation, and even without access to phase information focusing on a single as well as on multiple targets is demonstrated. Second, it is shown that the channel diversity, which dominates the achievable capacity of information transfer, can be optimized by tweaking the environment’s disorder; perfectly orthogonal channels are obtained without any software or hardware efforts on the transmit or receive side, and the benefits of the implied minimal cross-talk are illustrated for the scenario of wirelessly transmitting a full-color image. Third, the matrix formalism is leveraged to propose a scheme of analog computation that counter-intuitively uses a disordered instead of a carefully tailored propagation medium, by appropriately shaping the incident wave front. A proof-of-concept demonstration suggests that combining ubiquitous Wi-Fi hardware in an indoor environment with a simple metasurface is sufficient to implement the concept. Finally, the concept is also implemented in the optical domain using a multimode fiber. The third chapter outlines a few applications for sensors in context-aware environments. First, it is shown that by shaping ambient wave fields, they may be concentrated on harvesting devices to increase the output voltage available for sensor powering; moreover, the non-linear nature of the harvesting device enables to do so without direct feedback from the target, using indirect feedback from the second harmonic. Second, a smart around-the-corner motion detector for complex environments is presented, enjoying a co-design of hardware and processing software by using a dynamic metasurface aperture; the latter is essentially a small (but still electrically large) disordered cavity with tunable boundaries that leaks tunable random radiation patterns that couple differently to the environment’s modes. Third, it is shown that objects may be precisely localized in complex environments even if they are non-cooperative by establishing signatures of their location that leverage their scattering contribution; this is demonstrated both with a frequency diverse and a wavefront shaping scheme, and the equivalence of the respective degrees of freedom is established
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Hein, Hoernig Ricardo Oliver. "Green's functions and integral equations for the Laplace and Helmholtz operators in impedance half-spaces." Phd thesis, Ecole Polytechnique X, 2010. http://pastel.archives-ouvertes.fr/pastel-00006172.
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Dans cette thèse on calcule la fonction de Green des équations de Laplace et Helmholtz en deux et trois dimensions dans un demi-espace avec une condition à la limite d'impédance. Pour les calculs on utilise une transformée de Fourier partielle, le principe d'absorption limite, et quelques fonctions spéciales de la physique mathématique. La fonction de Green est après utilisée pour résoudre numériquement un problème de propagation des ondes dans un demi-espace qui est perturbé de manière compacte, avec impédance, en employant des techniques des équations intégrales et la méthode d'éléments de frontière. La connaissance de son champ lointain permet d'énoncer convenablement la condition de radiation dont on a besoin. Des expressions pour le champ proche et lointain de la solution sont données, dont l'existence et l'unicité sont discutées brièvement. Pour chaque cas un problème benchmark est résolu numériquement. On expose étendument le fond physique et mathématique et on inclut aussi la théorie des problèmes de propagation des ondes dans l'espace plein qui est perturbé de manière compacte, avec impédance. Les techniques mathématiques développées ici sont appliquées ensuite au calcul de résonances dans un port maritime. De la même façon, ils sont appliqués au calcul de la fonction de Green pour l'équation de Laplace dans un demi-plan bidimensionnel avec une condition à la limite de dérivée oblique.
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Schreiber, Adam W. "Formulation of integral equations using analytic Green's functions in elliptic cylindrical and prolate spheroidal coordinates." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1202499531/.
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Pavosevic, Fabijan. "Explicitly Correlated Methods for Large Molecular Systems." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/82000.
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Wave function based electronic structure methods have became a robust and reliable tool for the prediction and interpretation of the results of chemical experiments. However, they suffer from very steep scaling behavior with respect to an increase in the size of the system as well as very slow convergence of the correlation energy with respect to the basis set size. Thus these methods are limited to small systems of up to a dozen atoms. The first of these issues can be efficiently resolved by exploiting the local nature of electron correlation effects while the second problem is alleviated by the use of explicitly correlated R12/F12 methods. Since R12/F12 methods are central to this work, we start by reviewing their modern formulation.
Next, we present the explicitly correlated second-order Mo ller-Plesset (MP2-F12) method in which all nontrivial post-mean-field steps are formulated with linear computational complexity in system size [Pavov{s}evi'c et al., {em J. Chem. Phys.} {bf 144}, 144109 (2016)]. The two key ideas are the use of pair-natural orbitals for compact representation of wave function amplitudes and the use of domain approximation to impose the block sparsity. This development utilizes the concepts for sparse representation of tensors described in the context of the DLPNO-MP2 method by Neese, Valeev and co-workers [Pinski et al., {em J. Chem. Phys.} {bf 143}, 034108 (2015)]. Novel developments reported here include the use of domains not only for the projected atomic orbitals, but also for the complementary auxiliary basis set (CABS) used to approximate the three- and four-electron integrals of the F12 theory, and a simplification of the standard B intermediate of the F12 theory that avoids computation of four-index two-electron integrals that involve two CABS indices. For quasi-1-dimensional systems (n-alkanes) the bigO{N} DLPNO-MP2-F12 method becomes less expensive than the conventional bigO{N^{5}} MP2-F12 for $n$ between 10 and 15, for double- and triple-zeta basis sets; for the largest alkane, C$_{200}$H$_{402}$, in def2-TZVP basis the observed computational complexity is $N^{sim1.6}$, largely due to the cubic cost of computing the mean-field operators. The method reproduces the canonical MP2-F12 energy with high precision: 99.9% of the canonical correlation energy is recovered with the default truncation parameters. Although its cost is significantly higher than that of DLPNO-MP2 method, the cost increase is compensated by the great reduction of the basis set error due to explicit correlation.
We extend this formalism to develop a linear-scaling coupled-cluster singles and doubles with perturbative inclusion of triples and explicitly correlated geminals [Pavov{s}evi'c et al., {em J. Chem. Phys.} {bf 146}, 174108 (2017)]. Even for conservative truncation levels, the method rapidly reaches near-linear complexity in realistic basis sets; e.g., an effective scaling exponent of 1.49 was obtained for n-alkanes with up to 200 carbon atoms in a def2-TZVP basis set. The robustness of the method is benchmarked against the massively parallel implementation of the conventional explicitly correlated coupled-cluster for a 20-water cluster; the total dissociation energy of the cluster ($sim$186 kcal/mol) is affected by the reduced-scaling approximations by only $sim$0.4 kcal/mol. The reduced-scaling explicitly correlated CCSD(T) method is used to examine the binding energies of several systems in the L7 benchmark data set of noncovalent interactions.
Additionally, we discuss a massively parallel implementation of the Laplace transform perturbative triple correction (T) to the DF-CCSD energy within density fitting framework. This work is closely related to the work by Scuseria and co-workers [Constans et al., {em J. Chem. Phys.} {bf 113}, 10451 (2000)]. The accuracy of quadrature with respect to the number of quadrature points has been investigated on systems of the 18-water cluster, uracil dimer and pentacene dimer. In the case of the 18-water cluster, the $mu text{E}_{text{h}}$ accuracy is achieved with only 3 quadrature points. For the uracil dimer and pentacene dimer, 6 or more quadrature points are required to achieve $mu text{E}_{text{h}}$ accuracy; however, binding energy of $<$1 kcal/mol is obtained with 4 quadrature points. We observe an excellent strong scaling behavior on distributed-memory commodity cluster for the 18-water cluster. Furthermore, the Laplace transform formulation of (T) performs faster than the canonical (T) in the case of studied systems. The efficiency of the method has been furthermore tested on a DNA base-pair, a system with more than one thousand basis functions.
Lastly, we discuss an explicitly correlated formalism for the second-order single-particle Green's function method (GF2-F12) that does not assume the popular diagonal approximation, and describes the energy dependence of the explicitly correlated terms [Pavov{s}evi'c et al., {em J. Chem. Phys.} {bf 147}, 121101 (2017)]. For small and medium organic molecules the basis set errors of ionization potentials of GF2-F12 are radically improved relative to GF2: the performance of GF2-F12/aug-cc-pVDZ is better than that of GF2/aug-cc-pVQZ, at a significantly lower cost.<br>Ph. D.
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Cheng, Ching-Chung. "Investigations into Green's function as inversion-free solution of the Kriging equation, with Geodetic applications." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1095792962.
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Thesis (Ph. D.)--Ohio State University, 2004.<br>Title from first page of PDF file. Document formatted into pages; contains ix, 125 p.; also includes graphics (some col.). Includes bibliographical references (p. 101-103).
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Geng, Weihua. "Interface method and Green's function based Poisson Boltzmann equation solver and interface technique based molecular dynamics." Diss., Connect to online resource - MSU authorized users, 2008.
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Fares, Nabil F. (Nabil Fares). "Green's functions for plane-layered elastostatic and viscoelastic regions with application to 3-D crack analysis." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14632.
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Seljan, Josip. "Modélisation électromagnétique rapide de structures SIW par équations intégrales." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S071/document.
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La demande pour des systèmes RF plus compacts avec des bandes plus larges a poussé l'exploration de bandes toujours plus hautes en fréquence forçant un transfert des technologies existantes et l'invention de nouvelles pour ces bandes. Parmi les principaux obstacles rencontrés dans cet effort, se trouvent le problème du confinement de champ, les pertes diélectriques importantes, et les difficultés d'intégration entre deux systèmes conçus avec une technologie différente. Afin de pallier à ces problèmes, plusieurs nouvelles technologies sont apparues durant ces deux dernières décennies. Une des plus prometteuse est le guide d'onde intégré au substrat (ou SIW pour Substrate Integrated Waveguide). Sa caractéristique principale est la possibilité d'intégrer les guides d'onde dans un substrat, le plus souvent en intégrant des cylindres métalliques ou diélectriques densément disposés, dans un substrat dont les faces, inférieure et supérieure, sont hautement conductrices. Cette technologie offre une liberté sans précédent à la gamme de systèmes pouvant être réalisés. La richesse de possibilités de designs, la robustesse et la solidité des performances ont conduit à un nombre très larges de systèmes SIW, certains d'entre eux trouvant place dans des applications commerciales. L'inconvénient de cette technologie provient du très grand nombre d'élément nécessaire et de la complexité de son agencement. Par conséquent, ils présentent un défi du point de vue d'un concepteur, nécessitant des analyses numériques et des optimisations. Les solveurs les plus couramment utilisés à cette fin sont basés sur la FÉM, la FDTD / FDFD et MoM, ou sur une fusion de plusieurs méthodes. Bien qu'ils soient à la hauteur pour une vaste gamme de structures, les plus rapides et plus précis sont très recherchés. Cette thèse porte sur une méthode numérique hybride adaptée à l'analyse d'une vaste gamme de structures SIW planaires. Elle repose sur une représentation efficace des champs dans des guides d'ondes à parois parallèles, chargés avec des diélectriques planaires simples ou multicouches contenant des cylindres ; elle permet la construction de systèmes linéaires dont les solutions donnent les amplitudes de champ post-dispersion. Ce problème est ce que nous appelons le mode-matching, et fournit des moyens de calcul rapide de champ en présence de cylindres métalliques et diélectriques. Étant donné qu'une part importante de ces dispositifs utilise des fentes rectangulaires étroites comme éléments de couplage et de rayonnement, nous proposons une approche basée sur les MoM pour leur analyse. Grâce à l'application du principe d'équivalence, chaque fente remplacée par des courants magnétiques équivalents; la procédure divise efficacement le problème le plus large en plusieurs plus petits, chacun appartenant à une région délimitée par des plaques PEC parallèles (un seul guide d'ondes à plans parallèles). En exerçant les conditions aux limites sur les surfaces des fentes et en effectuant la pondération Galerkin, on obtient un système linéaire dont les solutions sont les amplitudes des courants magnétiques. De là, nous procédons au calcul des quantités pertinentes telles que les paramètres S, Y et Z. Nous fournissons des critères empiriques pour choisir le nombre de modes / fonctions de base suffisantes pour une grande précision. En outre, nous présentons des techniques d'approximation et montrons comment exploiter les symétries inhérentes à des dispositifs SIW afin d'accélérer encore plus la méthode. Nous présentons les résultats de l'analyse de plusieurs structures SIW, obtenus par notre code en interne sur la base de la méthode exposée ici, et les comparons à ceux obtenus avec un solveur commercial standard. Les résultats obtenus montrent une excellente précision et efficacité de la méthode proposée. Le facteur d'accélération, la robustesse et la généralité en font un outil attrayant pour être utilisé dans la conception et l'optimisation des dispositifs SIW<br>With constant demand for larger band and more compact RF devices, the rapid shift to higher frequency regions, as high as the W-band (75 to 110 GHz), forces microwave designers to both transfer existing technologies to and invent new ones for these bands. The major obstacles encountered in this endeavour are the problem of efficient field confinement, problematic electrical contacts, high dielectric losses, and difficult integration between devices realized with different technologies, to name a few. To overcome these issues, several competing technologies emerged in the past two decades. One of the most promising is the substrate-integrated waveguide (SIW) paradigm. Its key feature is the possibility of integrating waveguides into substrates, most often done by embedding densely-packed metal and dielectric cylinders into substrates bounded by highly-conductive layers, e.g. PCB-type ones. This provides unprecedented freedom in the range of devices that can be realized. Though commonly planar, these devices may have sidewalls of almost arbitrary shape and can be easily integrated with ones realized in alternative technologies, such as the coplanar-waveguide or microstrip technology. The richness in design possibilities, robustness and solid performance has led to a very large number of SIW devices, some of them finding place in commercial applications. Unfortunately, they often comprise a large number of elements and have complex layouts. Hence, they present a challenge from a designer’s perspective, necessitating numerical analysis and optimization. The most common solvers used for that purpose are based on FEM, FDTD/FDFD, and MoM, or merge several methods. Though they are up to the task for a vast range of structures, faster and more accurate ones are highly sought for. This thesis is concerned with a hybrid numerical method suited to the analysis of a vast range of planar SIW structures. It relies on an efficient representation of fields in parallel-plate waveguides, loaded with either single or multi-layer planar dielectrics, containing circular cylindrical posts; it enables the construction of linear systems whose solutions yield post-scattered field amplitudes. This problem is what we refer to as mode-matching, and provides means of fast computation of field in presence of metal and dielectric posts. Since a significant share of such devices use narrow rectangular slots as coupling and radiating elements, we propose an MoM-based approach to their analysis. Through the application of the equivalence principle, each slot replaced by equivalent magnetic currents; the procedure effectively partitions the larger problem into several smaller ones, each pertaining to a region bounded by parallel PEC plates (a single parallel-plate waveguide). Enforcing the boundary conditions at surfaces of slots and performing Galerkin weighting, we obtain a linear system whose solutions are the amplitudes of magnetic currents. From there we proceed to the computation of relevant quantities such as S, Y and Z parameters. We provide empirical criteria for choosing the number of modes/basis functions sufficient for high accuracy. Moreover, we present approximation techniques and show how to exploit symmetries inherent in SIW devices to speed up the method even further. To stress the features rendering our approach advantageous over the alternatives,we compare it to ones found in literature representing what we believe to be the most successful attempts. We present the results of analysis of several SIW structures of varying complexity, obtained by our in-house code based on the method exposed here, and compare them against the ones obtained with a standard commercial solver. The obtained results show excellent accuracy and efficiency of the proposed method. The speed-up factor, the robustness and generality make it an attractive tool to be used in design and optimization of SIW devices
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Gustafsson, Alexander. "Quantum point contact : A theoretical study." Thesis, Växjö University, School of Mathematics and Systems Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-6571.
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<p>Experiments shows that the conductance of a quantum point contact is quantized in steps of 2e²/h, where e is the charge of the electron and h is Planck’s constant, and thereby Ohm’s law is not valid for nanostructures. By using the approximation method finite difference, the transmission for one-dimensional contacts and one- and two-dimensional potentials are investigated. In the case of two-dimensional contacts and a two-dimensional potential the Green’s function method is used. It turns out that if electrons are treated as waves, the transmission and the conductance just differ by the constant 2e²/h, which in this thesis is interpreted numerically in Matlab by using the Green’s function method.</p>
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Rockway, John Dexter. "Integral equation formulation for object scattering above a rough surface /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/5832.
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Sternbeck, André. "The infrared behavior of lattice QCD green's functions a numerical study of lattice QCD in Landau gauge /." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981291910.
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Han, Feng. "Development of Novel Green’s Functions and Their Applications to Multiphase and Multilayered Structures." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1147874663.
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Bressler, Barry Lee. "An application of the Liouville resolvent method to the study of fermion-boson couplings." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/49994.
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The Liouville resolvent method is an unconventional technique used for finding a Green function for a Hamiltonian. Implementation of the method entails the calculation of commutators of a second-quantized Hamiltonian operator with particular generalized stepping operators that are elements of a Hilbert space and that represent transitions between many-particle states. These commutators produce linear combinations of stepping operators, so the results can be arrayed as matrix elements of the Liouville operator L̂ in the Hilbert space of stepping operators. The resulting L̂ matrix is usually of infinite order, and in principle its eigenvalues and eigenvectors can be used to construct the Green function from the L̂ resolvent matrix. Approximations are usually necessary, at least in the form of truncation of the L̂ matrix, and if one produces a sequence of such matrices of increasing order and calculates the eigenvalues and eigenvectors of these matrices, a sequence of approximations for the L̂ resolvent matrix can be produced. This sequence is mathematically guaranteed to converge to the exact result for the L̂ resolvent matrix (except at its singularities). The accuracy of an approximation depends on the order of the matrix at which the sequence is truncated.
Application of the method to a Hamiltonian representing interactions between fermions and bosons involves complications arising from the large number of terms generated by the commutation properties of boson operators.
This dissertation describes the method and its use in the study of fermion-boson couplings. Approximations to second order in stepping operators are calculated for simplified Froehlich and Lee models. Limited thermodynamic results are obtained from the Lee model. Exact energy eigenvalues are obtained by operator algebra for simplified Froehlich, Lee and Dirac models. These exact solutions comprise the main contribution of this research and will prove to be valuable starting points for further research. Suggestions are made for further research.<br>Ph. D.<br>incomplete_metadata
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Zhang, Yan. "Analysis of Elastic and Electrical Fields in Quantum Structures by Novel Green's Functions and Related Boundary Integral Methods." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1290184113.
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Hadziioannou, Céline. "Ondes sismiques en milieu complexe : mesure des variations temporelles des vitesses." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENU001/document.
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La thèse se concentre sur le suivi temporel des vitesses sismiques, notamment dans des zones de faille actives. En corrélant les signaux générés par le bruit ambiant, il est possible d'estimer la fonction de Green du milieu. Par le suivi continu de ces fonctions, des changements de vitesse dans le milieu peuvent être détectés. Les méthodes de suivi temporel sont appliquées aux données provenant d'une zone de faille active à Parkfield, Californie, ce qui permet de détecter deux chutes de vitesse. Ces dernières coïncident avec des évènements sismiques régionaux, la plus importante concernant un évènement proche des stations. Les deux chutes de vitesse sont suivies d'une récupération postsismique progressive. Pour mieux comprendre la fiabilité des mesures on a effectué des expériences en laboratoire. Un résultat intéressant de ces expériences montre que la reconstruction exacte de la fonction de Green n'est pas nécessaire pour le suivi temporel, ce qui ouvre la voie à de nombreuses possibilités d'applications en sismologie. Grâce à cette connaissance, la série de données de Parkfield a été ré-analysée. En améliorant la résolution temporelle à 1 journée, on montre que la chute de vitesse observée est cosismique avec le séisme de Parkfield. On a établi que les fluctuations de vitesse ne sont pas simplement corrélées aux variations de la distribution de sources du bruit obtenue par formation de voies. Enfin, les méthodes développées sont appliquées à un séisme au Japon. Le réseau étant de taille beaucoup plus grande que celui utilisé pour l'étude de Parkfield, ces données sont analysées pour étudier la dépendance entre la distance stations-séisme et la chute de vitesse mesurée<br>The thesis concentrates on monitoring seismic speeds, especially in active fault zones. By correlating signals generated by background noise, one can estimate the Green's function of a medium. When continuously following these functions, wave speed changes in the medium can be detected. Monitoring methods are applied to data from an active fault zone in Parkfield, California, where two wave speed drops, which coincide with regional seismic events, are detected. The largest corresponds to an event close to the stations. Both speed drops are followed by a gradual postseismic relaxation. In order to understand the reliability of the measurements, we perform laboratory experiments. One interesting result of these experiments shows that an exact reconstruction of the Green's function is not necessary for monitoring, which opens up many possibilities of applications to seismology. Armed with this knowledge, the Parkfield data is analysed again. By improving the temporal resolution to 1 day, we show that the observed speed drop is coseismic with the Parkfield event. We establish that the speed fluctuations are not simply correlated to variations in noise source distribution obtained by beamforming. Finally, the developed methods are applied to an event in Japan. Since the array is spatially much larger than the one used at Parkfield, this data is analyzed to study the dependence between station-event distance and the measured seismic speed drop. STAR